This invention relates to processes for preparing unsaturated phosphoric acid esters. In particular, this invention pertains to phosphoric acid esters prepared by reacting phosphoric acid with an epoxy acrylate and to the use of these materials as radiation curable monomers.
Epoxy acrylates, i.e., the reaction products of acrylic acid with diepoxide compounds, are described in U.S. Pat. No. 3,450,613. Resins made from bis-acrylate esters of phosphoric acid are described in U.S. Pat. Nos. 3,847,846; 4,001,150 and 4,291,097. Phosphate esters of epoxy resins are described in U.S. Pat. Nos. 4,164,487; 4,289,812 and 4,316,922.
A large number of phosphate ester compositions, including phenol bis-acrylate types and bisphenol related monoacrylates, in combination with ultraviolet sensitizers, are disclosed in U.S. Pat. No. 4,259,117. Such compositions are made by reacting unsaturated hydroxyl compounds with halophosphates.
Photocurable acrylic phosphate esters of epoxidized polybutadiene are described in U.S. Pat. No. 4,250,007. Such compositions are made by reacting the epoxidized polybutadiene with the reaction product of polycarboxylic acids or anhydrides with hydroxyethylacrylate plus acid phosphoric dimethacrylate or acid butyl phosphate monoester.
One of the major problems in radiation curable systems has been their poor adhesion to metal due in part to the low curing energy and to the resulting shrinkage of the cured film on the metal substrate. Although it is known that phosphorous containing compositions have improved adhesion to metal, it has been difficult to incorporate phosphoric acid itself into radiation curable systems.
Accordingly, it is an object of this invention to prepare radiation curable coating compositions having good adhesion to metal.
It is another object of this invention to prepare compositions which may be used as radiation curable monomers.
It is a further object of this invention to prepare stable phosphoric acid esters of acrylate or methacrylate esters of epoxide resins.
These and other objectives are obtained by preparing the compositions of the instant invention.